In the prior art many types of detectors have been utilized for demodulating frequency and phase modulated carrier signals. One particular type of detector is a differential detector. A differential detector utilizes a delay element to delay an intermediate frequency (IF) frequency or phase modulated signal input to the detector, and the delayed signal is then mixed with the undelayed signal to demodulate the IF signal. The detector output signal is then passed through a filter leaving only the desired demodulated signal. In these prior art differential detectors the element providing the signal delay is usually the most significant part of the detector. At frequencies above in the order of 50 MHz delay lines and lumped delay networks as delay elements are practical and may be used as the delay element. At frequencies below in the order of 50 MHz delay lines are impractical as delay elements in that they are too bulky and expensive. Digital delay elements such as shift registers are practical up to approximately 2 MHz. There are no practical delay elements that can be used in differential detectors between approximately 2 MHz and 50 MHz. Thus, there is a need to solve the problem of expensive and bulky delay elements and secondarily to solve the frequency limitation problem of prior art detectors.
My invention solves these problems in the prior art. I provide a differential detector that doesn't utilize its own delay element as is done in the prior art, and can operate at frequencies heretofore impractical in the prior art. By deleting the delay element a cost savings is realized as it is often the most significant cost item in the detector. A space savings is also realized because the delay element is eliminated, and when the delay element is a delay line the space savings is appreciable.